Replacement of cervical discs with synthetic devices that preserve motion could destabilize the cervical spine. Trauma to a destabilized cervical spine could cause spine cord injury. Insertion of most types of artificial disc replacements (ADR) requires cutting the anterior longitudinal ligament and removal of a portion of the anterior half of the annulus fibrosis and nucleus pulposus. Weakening the supporting structures on the anterior portion of the spine increases the probability of spinal cord injury with excessive force from a posterior direction. For example, a patient with an ADR in the cervical spine could become paralyzed from “whiplash” resulting from a motor vehicle accident.
Inventions do exist to help prevent the extrusion of ADR materials. For example, U.S. Pat. No. 6,063,121 teaches the use of x-shaped wires about the entire perimeter of the upper and lower plates. Lastly, '121 teaches the use of “wires” in a repeating X pattern. Our preferred embodiment of the device should include other, more flexible materials. Check reins made of inelastic, materials that do not flex well, will limit ADR motion excessively. Circumferential check reins must become lax, allowing the ADR Endplates to approach one another, to permit ADR motion. Repeated bending of wires risks injury to the surrounding tissues. First, the bend in stiff wires could impinge the surrounding tissues. Second, the tissues could be pierced by the ends of broken wires.
Similarly, U.S. Pat. No. 3,867,728 teaches the use of Dacron stitching in an X pattern about the periphery of ADRs. U.S. Pat. Nos. 4,911,718; 5,171,281; and 5,545,229 show the use of outer elastic membranes that are reinforced with fibers. The membranes are placed such that the reinforcement fibers are oriented in a crossing pattern between membranes.